A peak detector is an analog circuit adapted to detect the peak levels of a signal. A peak detector with a reset capability is commonly referred to as an envelope detector. Envelope detectors are widely used in gain control and spectral energy estimation. Many of the conventional envelope detectors can only operate at low to middle frequency bands, e.g., 1 kHz to 10 kHz, and low to middle data rate applications.
Envelope detectors can be used to generate an output signal representing the envelope level or amplitude of a high frequency input signal. This can be used in many applications, such as demodulating an amplitude modulated input signal, detecting the strength of a received radio frequency (RF) signal, detecting the level of a generated RF signal for use in amplitude leveling loops, detecting the level of a generated RF signal for use in an amplitude feedback loop such as in a polar modulator, or for other suitable applications.
Envelope detection circuitry is typically implemented in high speed serial communication circuitry such as, for example, that defined in accordance with the USB standard. Generally, an envelope detection circuitry in a high-speed serial link detects the envelope of the amplitude of the high frequency input signal and generates an output signal if the amplitude exceeds a threshold to differentiate from un-driven or tri-stated differential inputs.